As diesel engines become predominant in Europe and begin to gain increased consideration in the US, Delphi says that it has an answer to the question of helping automakers answer a tough question: how can the industry meet stricter emission standards without compromising cost, fuel efficiency and engine performance?
An answer, the company says, is to create an on-board diesel fuel reformer that uses air to convert diesel fuel into a hydrogen-rich reformate during a catalytic partial-oxidation process.
With this design, Delphi claims that its reformer can help reduce cost and performance trade-offs while being robust enough to help meet future Euro VI and U.S. Tier II-Bin 5 standards.
Dr. Jean (John) Botti, business line executive for Delphi’s powertrain systems, discussed the fuel reformer during a panel entitled, “Hybrids vs. Diesel vs. Modified Gasoline, the Near Term – Is It Time for a Reality Check?” at the SAE conference yesterday.
“We all agree that diesel has enormous potential worldwide,” Botti said. “Of all the current fuel and propulsion alternatives, diesel holds the best near-term promise. However, it is imperative to develop a cost-effective emission solution that helps maintain the diesel engine as a leader in fuel economy and performance.”
“Delphi’s diesel fuel reformer is a unique approach to help meet future emission standards,” Botti added. “We believe that, in time, our approach will provide our customers with an economical, realistic solution to help reduce vehicle emissions. It will help them increase diesel market share in Europe and in the U.S.”
Future diesel emission challenges are becoming increasingly complex, with the stringent NOx and particulate matter (PM) standards. Since diesel engines run lean, reducing NOx requires a reductant. One known reducing agent is ammonia generated from urea, which is used with a Selective Reduction Catalyst (SCR) and requires an appropriate dispensing infrastructure. An alternative approach is the use of a NOx adsorber or NOx trap that frequently needs to be regenerated.
Delphi’s approach utilises an on-board fuel reformer that converts diesel fuel into hydrogen-rich reformate using air in a catalytic partial oxidation process. The reformate, rich in hydrogen and carbon monoxide, is used to regenerate and desulfate NOx adsorbers. This process, the company says, is ‘far superior in many respects’ than using the diesel fuel as a reductant. Reformate also is used for diesel particulate filter regeneration.
The reformer system produces reformate on-demand and injects it directly into the exhaust system without requiring the engine to operate at a rich A/F ratio. Thermal management of exhaust components can also be achieved using reformate when injected into exhaust catalysts under lean conditions.
The fuel reformer has the potential to reduce cost due to the reduction of the catalyst volume and PGM loading of a NOx adsorber and particulate trap, says Delphi. In addition, the ability for reformate to improve the low temperature performance of the NOx adsorber, and the ability to provide heat, helps reduce the need for costly energy-conserving exhaust system components and engine generated heating strategies, the company claims.
Delphi’s objective is to provide solutions that would require no additional on-board fluids, such as urea. Preliminary results obtained by Delphi on a mule truck indicate that the reformer can indeed enable meeting Tier2 Bin5 standards using a NOx adsorber.
“This will be a definitive advantage,” Botti added. “We do not need any additional inventions; we just need to put our emerging technology into practice.”
Delphi engineers believe this technology will help high displacement diesel powertrains compete in the US market with gasoline hybrids since it will provide high fuel economy and extremely favorable emission benefits. The technology, currently under development, is targeted to be available in the marketplace when 100 percent compliance to Tier2 Bin5 fleet average begins in 2009.